A study is being made of chemically- or electrically-induced seizure activity in mouse brain. Work to date has indicated that elevated cyclic GMP concentrations in the cerebellum are associated with many types of seizures, and that when convulsions are suppressed by drugs, cyclic GMP is decreased. In addition, increased GABA concentrations may be involved in anticonvulsant action. Studies on whole mouse brain indicate that a major locus of action of phenytoin is in the cerebellum. Microdissection and microanalytical procedures have been used to analyze both cerebellar and cortical layers after electroshock and isoniazid incuced seizures, and in the presence of anticonvulsants